Method for transferring wireless power

ABSTRACT

This invention defines management protocols for wireless power transfer to multiple devices in Multi-device Wireless Power Management System. Various functions of Multi-device Wireless Power Management System are justified from this invention. The WPT frames and messages which work between the management block of a charger and the management block or the coupler block of a device, or the coupler block of a charger are defined as well to execute various functions. Also the procedures for each functionality are described based on its frames and messages.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. application Ser. No. 14/255,641, filed Apr.17, 2014, which claims priority under 35 U.S.C. §119 to U.S. PatentApplication No. 61/812,879, filed on Apr. 17, 2013, the disclosure ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method and a system for transferringwireless power, more particularly, to a method and a system which definemanagement protocols for wireless power transfer to multiple devices inMulti-device Wireless Power Management System.

BACKGROUND

A wireless charging system using a magnetic induction phenomenon aswireless power transmission technologies wirelessly transmitting energyhas been used.

For example, an electric toothbrush, a cordless razor, or the like, ischarged by a principle of electromagnetic induction. In recent years,wireless charging products capable of charging portable devices such asmobile phones, PDAs, MP3 players, notebook computers, or the like, usingthe electromagnetic induction have been released.

However, the magnetic induction scheme inducing current through magneticfield from a single coil to another coil is very sensitive to a distancebetween the coils and a relative position of the coils to sharplydegrade transmission efficiency even when the distance between two coilsare slightly spaced or twisted from each other. Therefore, the wirelesscharging system according to the magnetic induction scheme may be usedonly in a short range of several centimeters or less.

Meanwhile, U.S. Pat. No. 7,741,734 discloses a method of wirelessnon-radiative energy transfer using coupling of resonant-fieldevanescent tails. The basis of this technique is that two same-frequencyresonant objects tend to couple, while interacting weakly with otheroff-resonant environmental objects, which makes it possible to transferenergy farther away compared to the prior art magnetic induction scheme.

There are the complexity and inconvenience of wire cable chargers bytransferring power wirelessly.

SUMMARY

This invention provides management protocols for wireless power transferto multiple devices in Multi-device Wireless Power Management System.Various functions of Multi-device Wireless Power Management System arejustified from this invention. The WPT frames and messages which workbetween the management block of a charger and the management block orthe coupler block of a device, or the coupler block of a charger aredefined as well to execute various functions. Also the procedures foreach functionality are described based on its frames and messages.

This invention defines management protocols for wireless power transferto multiple devices in Multi-device Wireless Power Management System.Various functions of management protocols are justified from thisinvention. The frame format and the messages are defined as well toexecute functions. Also the procedures for each functionality aredescribed based on its frame format and messages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the wireless power transfer system.

FIG. 2 is a diagram illustrating MPAN applied to mobile devices.

FIG. 3 is a diagram illustrating MPAN applied to home appliances.

FIG. 4 is a diagram illustrating MPAN superframe structure.

FIG. 5 is a diagram illustrating PSFI in response period.

FIG. 6 is a diagram illustrating MPAN physical element.

FIG. 7 is a diagram illustrating MPAN-C state diagram.

FIG. 8 is a diagram illustrating MPAN-N state diagram.

FIG. 9 is a diagram illustrating PHY layer frame format.

FIG. 10 is a diagram illustrating preamble format.

FIG. 11 is a diagram illustrating MAC layer frame format of MPAN.

FIG. 12 is a diagram illustrating format of command frame.

FIG. 13 is a diagram illustrating payload format of request frame.

FIG. 14 is a diagram illustrating block format of power transferrequest.

FIG. 15 is a diagram illustrating block format of power transfer beaconrequest.

FIG. 16 is a diagram illustrating payload format of response frame.

FIG. 17 is a diagram illustrating block format of power transferresponse.

FIG. 18 is a diagram illustrating payload format of acknowledgementframe.

FIG. 19 is a diagram illustrating block format of power transferresponse confirmation.

FIG. 20 is a diagram illustrating block format of power transfer requestcommand confirmation.

FIG. 21 is a diagram illustrating block format of power transferexecution command confirmation.

FIG. 22 is a diagram illustrating block format of power level requestcommand confirmation.

FIG. 23 is a diagram illustrating payload format of command frame.

FIG. 24 is a diagram illustrating block format of power transfer requestcommand.

FIG. 25 is a diagram illustrating block format of power transferexecution command.

FIG. 26 is a diagram illustrating block format of power level requestcommand.

FIG. 27 is a diagram illustrating MAC layer frame format for WPT.

FIG. 28 is a diagram illustrating control field.

FIG. 29 is a diagram illustrating payload format of PS beacon.

FIG. 30 is a diagram illustrating payload format of PSF.

FIG. 31 is a diagram illustrating procedure in stabilization (withouterror).

FIG. 32 is a diagram illustrating procedure in stabilization (errordetection).

FIG. 33 is a diagram illustrating procedure in invigoration.

FIG. 34 is a diagram illustrating procedure in revitalization.

FIG. 35 is a diagram illustrating WPT signal.

DETAILED DESCRIPTION OF EMBODIMENTS

The advantages, features and aspects of the present invention willbecome apparent from the following description of the embodiments withreference to the accompanying drawings, which is set forth hereinafter.The present invention may, however, be embodied in different forms andshould not be construed as limited to the embodiments set forth herein.Rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the presentinvention to those skilled in the art.

The terms used herein are for the purpose of describing particularembodiments only and are not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof. Hereinafter, embodiments ofthe present invention will be described in detail with reference to theaccompanying drawings.

Information technology—Telecommunications and information exchangebetween systems—Magnetic field area network (MFAN) Part 2: In-bandcontrol protocole for wireless power transfer

1. Scope

This invention establishes a system for an in-band network, from whichboth wireless power transfer and data transmission are carried outsimultaneously at a same frequency band. It provides technical solutionfor a remote and consistent power supply along with a stable network.

For the purpose of this invention, the system is designed based on theprinciples described in ISO/IEC 15149 (Magnetic Field Area Network). Inthis way, it is expected to achieve superiority in control of devices,while managing wireless power transfer to multiple devices in request.The focus is on the physical and media access control layer protocol; itwill not discuss matters on the upper layer protocols. As together, thePHY and MAC layers should be able to carry out the following tasks: datatransmission, signal control, wireless power transfer.

This invention is applicable in various situations and environments, butis expected to perform in excellent in certain use cases:

1) Mobile phones: provide ubiquitous charging environments for portabledevices

2) Home appliances: allow unrestrained placement of appliances with theelimination of wire cables and plugs for power supply

The media access control layer protocol is designed for the followingscope:

1) Variable superframe structure for wireless power transfer to multipledevices

2) Simple and effective network topology for efficient wireless powertransfer

3) Dynamic address assignment for efficient timesharing among multipledevices

The physical layer protocol is designed for the following scope:

1) One frequency band for both wireless power transfer and magneticfield communication

2) Simple and robust modulation for low-cost implementation andminimized margin of error

3) Variable coding and bandwidth for dynamic charging environment

2. Normative References

The following referenced documents are indispensable for the applicationof this document. For dated references, only the edition cited applies.For undated references, the latest edition of the referenced document(including any amendments) applies.

ISO/IEC 15149-1, Information technology—Telecommunications andinformation exchange between systems—Magnetic field area network(MFAN)—Part 1: Air Interface

3. Terms and Definitions

For the purposes of this document, the following terms and definitionsapply.

3.1 Wireless Power Transfer (WPT)

Method of consistent and simultaneous power supply to multiple deviceswithin a range without physical contact

3.2 Magnetic Field Area Network (MFAN)

Specified in ISO/IEC 15149-1

3.3 Magnetic Power Network (MPAN)

In-band wireless power transfer network that incorporates magnetic fieldarea network (MFAN) in its communication and wireless power transferwithin a single frequency band

3.4 Magnetic Power Area Network—Coordinator (MPAN-C)

Device that carries out integral operations for magnetic power areanetwork; wireless power transfer, connection and release of devices, andtime scheduling of power transfer and data

3.5 Magnetic Power Area Network-Node (MPAN-N)

Devices that comprises magnetic power area network, and that is not acoordinator

4 Symbols and Abbreviated Terms

The following acronyms are used in this document:

ARq Association Request

ARs Association Response

ARA Association Response Acknowledgement

ASC Association Status Check

ASK Amplitude Shift Keying

ASRq Association Status Request

ASRs Association Status Response

ASRA Association Status Response Acknowledgement

BPSK Binary Phase Shift Keying

CRC Cyclic Redundancy Check

DA Data Acknowledgement

DaRq Disassociation Request

DaRs Disassociation Response

DaRA Disassociation Response Acknowledgement

DRq Data Request

DRs Data Response

DRA Data Response Acknowledgement

FCS Frame Check Sequence

GSRq Group ID Set-up Request

GSRs Group ID Set-up Response

GSRA Group ID Set-up Response Acknowledgement

LSB Least Significant Bit

MAC Media Access Control

NRZ-L Non-Return-to-Zero Level

PHY Physical Layer Protocol

PLRC Power Level Request Command

PLRCA Power Level Request Command Acknowledgement

PS Power Status

PSF Power Status Feedback

PSFI Power Status Feedback Interval

PT Power Transfer

PTBRq Power Transfer Beacon Request

PTEC Power Transfer Execution Command

PTECA Power Transfer Execution Command Acknowledgement

PTPC Power Transfer Permission Command

PTRC Power Transfer Request Command

PTRq Power Transfer Request

PTRs Power Transfer Response

RA Response Acknowledgement

RR Response Request

SIFS Short Inter Frame Space

TDMA Time Division Multiple Access

UID Unique Identifier

5 Overview

MPAN is an in-band wireless network system that enables wirelesscommunication and wireless power transfer within a single frequencyband. Data and control commands are communicated according to the MFANsystem; power is transferred wirelessly according to the consistant WPTsystem, both at the same frequency band. Due to the characteristics ofmagnetic field and legal regulations on the power level, the range ofMFAN is wider than that of WPT. Within the MPAN, the maximum WPTefficiency is achieved with an MPAN-C taking in charge of everyscheduling accordingly for devices in most effective orders.

The MFAN has a low carrier frequency bandwidth of 30 KHz to 300 KHz; thesame frequency band is used for WPT. It uses a simple and robustmodulation method like BPSK for low cost implementation and low errorprobability. Also dynamic coding methods like Manchester and NRZ-L areconsidered in specific against noises. It can provide data transmissionspeed of several kbps within a distance of several meters. For WPT,unmodulated sine sinusoidal signal is used to enhance WPT efficiency.The MPAN uses a simple and efficient network topology like the ‘startopology’ for low power consumption. It uses dynamic address assignmentfor small packet size, so to manage address efficiently as well. Also itincorporates an adaptive link quality control by using varioustransmission speeds, and coding methods suitable for various MPANenvironments.

There are two kinds of devices participating in an MPAN according totheir functions: MPAN-C and MPAN-N. Only one MPAN-C may exist within anMPAN, where a number of MPAN-Ns may be registered to. As a base stationof MPAN, MPAN-C manages connection and release of MPAN-Ns when there isresponse to its request. For the data transmission, MPAN uses TDMAmethod; When an MPAN-N joins MPAN managed by MPAN-C, MPAN-C allocatestime-slots for the MPAN-N. WPT and data transmission would begin asMPAN-C requests for the responses of MPAN-Ns.

As shown in FIG. 1, MPAN-C and MPAN-Ns are to be located elsewherewithin the network. If MPAN-C receives relevant data for WPT-ID, batteryinformation, etc.—from MPAN-Ns, it examines factors like power transfersequences or the number of time slots for an appropriate WPT. MPAN-Cthen sends control data back to MPAN-Ns to manage overall WPToperations.

MPAN can be applied to various industries. It may be applied to asituation where electric devices are in need of constant power supply tofunction properly. For some industries, significant improvement inefficiency is attainable simply by providing power wirelessly. In anycases, duration of battery life no longer becomes a problem; no need tospare broad space for spacious batteries and charging equipment.

As for an example, there has always been a battery issue when it comesto using mobile devices (FIG. 2) due to its running time. MPAN is ableto provide a ubiquitous charging environment while on a stable networkservice. Also for the home appliances (FIG. 3), complex wire cables andplugs can be eliminated; a placement of home appliances at one'sconvenience becomes possible with MPAN.

6 Network Elements

6.1 General

The elements of MPAN, based on the elements of MFAN, are classified intwo: time and physical element. The time element refers to thesuperframe structure consisting of request period, response period, andspontaneous period. The physical element refers to the MPAN devices:MPAN-C and MPAN-Ns. The most basic unit in the physical element isdevice. A device may be defined according to its role either as anMPAN-C that manages network, or an MPAN-N that communicates with MPAN-C.

When an MPAN is set up, a node is allocated to be an MPAN-C: the devicein charge of the perfect control of association, disassociation,release, and time scheduling for MPAN-Ns. The superframe begins when adevice is set as an MPAN-C, and starts to transmit request packetsduring the request period. Within MPAN, only a single channel ispermitted by an MPAN-C; the rest devices within the MPAN become MPAN-Ns.Note that a device within an MPAN may participate as an MPAN-C or MPAN-Ndepending upon its role. For the connection between an MPAN-C and anMPAN-N, a peer-to-peer connection is used.

6.2 Time Element

6.2.1 General

The MPAN inherits the same time elements used in MFAN, ISO/IEC 15149-1,which is much similar to the method used in TDMA time slot;

MPAN-C arranges times slots for individual MPAN-Ns. MPAN-C manages datafrom the group of MPAN-Ns during response period. There are some newfeatures newly introduced from 15149-2 in relation to WPT.

6.2.2 Time Element for MPAN

The time element of MPAN, as shown in FIG. 4, consists of requestperiod, response period, and spontaneous period. The lengths of requestand response period are varied; the length of spontaneous period issubject to the length of request and response period.

The superframe begins when MPAN-C transmits a PTRq packet to MPAN-Nsduring the request period. When MPAN-N receives the packet, it sendsPTRs packet back as a response. According to the PTRs packets received,MPAN-C sends PTBRq packet with information on the WPT time schedule. Inthat case, relevant MPAN-Ns can receive WPT during the followingresponse periods. During the power status feedback interval, MPAN-Nswill transmit the PSF packet as a response to the PS beacon from MPAN-C.

6.2.2.1 Request Period

During the request period, MPAN-C transmits PTRq packet to inviteMPAN-Ns to WPT time schedule. Receiving PTRq packet, MPAN-Ns prepare totake WPT from MPAN-C.

6.2.2.2 Response Period

The response period can be divided into several time slots by the numberof MPAN-Ns for WPT. The length of each time slot varies according to thetotal length of WPT. When MPAN-C schedules for a response period, MPAN-Callocates slot numbers to each time slots in a numerical order; if thereis not an

MPAN-N, the slot number will be zero. MPAN-C may assign each time sloteither to an individual MPAN-N or to a group of MPAN-Ns. According to asequence of the schedule, an MPAN-N or all the MPAN-Ns in a group mayreceive wireless power simultaneously.

During the response period of MPAN, MPAN-Ns send PTRs to MPAN-C if thenode is in need of WPT. The MPAN-Ns put in schedule by MPAN-C canreceive WPT during the response period. MPAN-C, with the informationreceived, calculates distance to MPAN-Ns. MPAN-C will then return PTBRqto MPAN-Ns to provide detailed time schedule and start WPT at a powerlevel appropriate for the distance.

Distinguishable to the MFAN response period, the response period of MPANhas PSFI. After each time slot, there is a PSFI for quick power statusupdate and abnormal situation. During WPT, when MPAN-N receives the PSbeacon in the PSFI, it transmits the PSF packet to MPAN-C for notifyingthe updated power status as the response for the PS beacon in the PSFI.When abnormal situation is sensed by the MPAN-C, it is notified to allMPAN-Ns in the PSFI by the MPAN-C. When the MPAN-Ns recognize error byreceiving the PS beacon, they wait until receiving a request from theMPAN-C.

6.2.2.3 Spontaneous Period

The spontaneous period begins when MPAN-C confirms all PSF packets fromMPAN-Ns in the last time slot of the response period and broadcastsPTPC. It will last until MPAN-C will transmit a RR packet again. Duringthis period, low power devices can request power transfer withoutMPAN-C's request. When MPAN-C receives PTRC packet, it returns PTECpacket. As MPAN-C receives PTECA, the acknowledgement, it provides WPTto low power devices for a certain length of time. Afterward, MPAN-C andMPAN-N sends PLRC and PLRCA correspondently to check on the power levelreceived. This period will last until MPAN-C transmits a request packet,or until it engages into a request period again.

6.3 Physical Element

There are two kinds of physical elements within MPAN, which are MPAN-Cand MPAN-N. The basic unit, device, can be categorized either as anMPAN-C or MPAN-N according to its role. An MPAN-C manages entire MPAN.An MPAN-C is able to control MPAN-Ns with RR packets. MPAN-Ns mustreturn response packets back accordingly to MPAN-C in order to proceedwith operations. A basic configuration of MPAN is shown in FIG. 6.

6.3.1 Coordinator

MPAN-C is a node that manages MPAN; there is only a single MPAN-C pernetwork. By transmitting an appropriate RR packet, it can manage andcontrol MPAN-Ns within MPAN.

6.3.2 Node

MPAN-N is a device that is associated to an MPAN, and is not an MPAN-C.As much as 65,519 MPAN-Ns can link to a network at the same time. Itreturns response packets according to the RR packet sent by MPAN-C.

6.4 Address Element

In order to identify MPAN-Ns, MPAN uses an address system for MFAN ID,UID, group ID, node ID, and charging ID.

6.4.1 MFAN ID

Specified in ISO/IEC 15149-1, 5.4.1

6.4.2 UID

Specified in ISO/IEC 15149-1, 5.4.2

6.4.3 Group ID

Specified in ISO/IEC 15149-1, 5.4.3

6.4.4 Node ID

Specified in ISO/IEC 15149-1, 5.4.4

6.4.5 WPT ID

WPT ID is an identifier used during WPT. The ID has an 8-bit addressassigned by MPAN-C for quick communication during WPT. The ID isallocated to MPAN-Ns during the request period right before WPT begins.Some WPT IDs are reserved in Table 3.

TABLE 1 Reserved charging ID Node ID Content Remarks 0xFF All nodes Whenbroadcasting or transmitting all nodes 0xFE Unjoined Default ID for nodenode 0xF0-0xFD Reserved —

7 Network Status

7.1 General

The MPAN inherits the same network status used in MFAN, ISO/IEC 15149-1.On top of it, there are some newly introduced statuses for MPAN inrelation to wireless power transfer: stabilization, invigoration,revitalization status.

7.2 Network Status for MPAN

7.2.1 Stabilization

MPAN in stabilization carries out wireless power transfer in everynormal condition. As MPAN-C sends PTRq packet during the request period,MPAN-Ns probe the packet and transmit PTRs packet accordingly during theresponse period. Based on the information in the PTRs packet, MPAN-Cschedules time slots for WPT and transmits the schedule in PTBRq packet.WPT will commence as MPAN-C transmits PTS beacon. MPAN-Ns receive WPTfrom MPAN-C according to the scheduling sequence during the responseperiod to MPAN-Ns in a time slot. After a time slot for WPT is finished,there is PSFI for quick power status update. When MPAN-Ns receive PSbeacon from MPAN-C during the PSFI, MPAN-Ns will send PSF packet uponMPAN-C's requests. After confirming the PSF packets, the MPAN-C willinform MPAN-Ns the start of WPT with PTS beacon, engaging in WPT for thenext time slot. During WPT, MPAN-C may stop WPT if it detects error.Otherwise, WPT is completed when MPAN-C receives every PSF packet fromthe last time slot.

7.2.2 Invigoration

MPAN in invigoration prioritizes devices low in power, and suppliespower during spontaneous period to keep them on-line. When an MPAN-Nbecomes low in power, the MPAN-N will operate in power-saving mode,minimizing its operations. The MPAN-N may request power supply to MPAN-Cin order to prevent shutting down. To do so, the MPAN-N will send PTRCto MPAN-C upon receiving PTPC; the MPAN-N will then receive returningPTEC from MPAN-C. MPAN-N will send PTECA and be engaged in WPT. The WPTto an MPAN-N low in battery is to be kept minimal, not to interruptoriginally scheduled WPT. If MPAN-N receives power up to a thresholdlevel (to be cut off from the WPT), the WPT will be terminated. Afterthe power transfer in invigoration, MPAN-C sends PLRC to check on thepower level received. MPAN-N will return PLRCA and if the power level isabove threshold 2, the status will then become stabilization.

7.2.3 Revitalization

MPAN in revitalization provides power transfer to unassociated devicescompletely dried up of power. MPAN system includes distinctive WPTscenario to power down devices. When an MPAN-N is run out of power, thedevice is unable to process any signaling operations. Therefore, MPAN-Cis unable to control the MPAN-N out of power; although it is notproperly scheduled and may interrupt current WPT, the MPAN-N out ofpower will receive WPT during response period. However, in spontaneousperiod, MPAN-C transmits PTEC (no ack.) and transfer power regularly, toreceive PLRCA for PLRC from revived power-down devices as soon aspossible. MPAN-C will then be able to manage and control the revivedMPAN-N and undergoes procedures explained from 7.2.2 invigoration.

7.3 MPAN State

MPAN device state includes MPAN-C state and MPAN-N state as justified inISO/IEC 15149-1. Put in detail, MPAN-C states are divided into standbystate, packet analysis state, packet generation state; power transferstate, power transfer standby state, power status packet analysis state,and power status packet generation state. MPAN-N states are composed ofhibernation power level detection state, stable hibernation state,general activation state, standby state, packet analysis state, packetgeneration state; power reception state, power isolation state, powerdown hibernation state, low power hibernation state, low power packetanalysis state, low power packet generation state, PSF activation state,power status packet analysis, power status packet generation.

7.3.1 Coordinator State

7.3.1.1 Communication Procedure

The state of MPAN-C will be at standby when power is turned on. Duringstandby state, the system commands transmission of RR packet and thesuperframe begins; MPAN-C enters packet generation state. Once thetransmission of RR packet is carried out, MPAN-C returns to standbystate, waiting for responses. When MPAN-C receives response (orwhichever packet) from MPAN-Ns while performing carrier detection duringstandby state, MPAN-C enters packet analysis state. If the destinationID of the received packet and the node ID of MPAN-C correspond, MPAN-Centers packet generation state. During packet generation state, MPAN-Cgenerates either RA or DA packet accordingly, and sends to MPAN-Ns. Thestate of MPAN-C will return to standby state, afterward.

In case of error detection within the data packet while on packetanalysis, the MPAN-C returns directly to standby state. If errors aredetected within the received response packet or destination ID of thereceived response packet do not corresponds to node ID of MPAN-C duringpacket analysis state, MPAN-C re-generates RR packet from generationstate and re-transmits it to MPAN-Ns after a certain length of time; theMPAN-C returns to standby state. If the failure continues, the procedurewill be repeated as many times as configured (maximum ofNtimes). On the(N+1) th attempt, MPAN-C returns to standby state from packet analysisstate.

7.3.1.2 Stabilization Procedure

For WPT, MPAN-C enters packet generation state as the superframe begins(system commands), and sends PTRq packet. Once the transmission of PTRqpacket is carried out, MPAN-C returns to standby state. When MPAN-Creceives PTRs packet from MPAN-Ns, MPAN-C enters packet analysis state.After confirming the packet, MPAN-C enters packet generation state tocreate PTBRq packet with the schedule for WPT. With the transmission ofPTBRq packet, MPAN-C enters power status packet generation state.MPAN-C, after sending PTBRq packet, again sends PTS to MPAN-Ns,informing the start of WPT according to the schedule provided; MPAN-Centers power transfer state.

MPAN-C enters power status packet generation state, when PSFI begins. AsMPAN-C transmits PS beacon to all MPAN-Ns during the PSFI, MPAN-C willenter power transfer standby state and receive PSF packets from MPAN-Ns.Receiving PSF packets, MPAN-C enters power status packet analysis state.From power status packet analysis, MPAN-C counts the number of PSFpackets and the number of time slots. If the number of PSF does notequal to the number of total PSF packets to be received, MPAN-C returnspower transfer standby, waiting for the next PSF packet. If the numberof PSF packets equal to the total number of PSF packets, MPAN-C countson the slot number. If slot number does not equal to the number of totalslots (last slot number), MPAN-C enters power status packet generationstate to re-send PTS beacon packet for the WPT in the next time slot. Ifthe slot number equals to the number of total time slots, it indicatesthe WPT time scheduling has finished for the response period; MPAN-Creturns standby state. For error detection during power transfer, MPAN-Cimmediately enters power transfer standby. MPAN-C waits until currenttime slot times-out, and enter power status packet generation for PSFI.

7.3.1.3 Invigoration Procedure

During invigoration, MPAN-C enters packet generation state as systemcommands to send PTPC to indicate the start of spontaneous period. MPANreturns to standby to wait for PTRC. When MPAN-C receives PTRC, MPAN-Centers packet analysis to check node ID. If it corresponds, MPAN-Centers packet generation to create PTEC (with ack.) and returns standby.Upon receiving PTECA, it goes packet analysis, then onto power transferstate to engage in power transfer to low power devices. When powertransfer times out in spontaneous period, MPAN-C enters standby. Afterevery power transfer in spontaneous period, MPAN-C check on the powerlevel received from the MPAN-Ns that received power. MPAN-C enters fromstandby to packet generation to generate PLRC. MPAN-C waits from standbyfor PLRCA. As MPAN-C receives PLRCA, it goes to packet analysis state,then returns standby.

7.3.1.4 Revitalization Procedure

During revitalization, MPAN-C enters packet generation at the beginningof spontaneous period as the system command, to generate PTEC (withoutack.) broadcasting. MPAN-N enters power transfer as MPAN-C sends PTEC;MPAN-C returns standby afterward. After the power transfer, the systemcommands to broadcast PLRC. MPAN-C will enter packet generation andstandby consecutively. On receipt of PLRCA, MPAN-C realizes MPAN-Ns inlow-power, and engages in invigoration.

The states of MPAN-C are as described on FIG. 7.

7.3.2 Node State

7.3.2.1 Communication Procedure

As MPAN-N is turned on, it will enter hibernation power level detectionstate. According to power level condition, it diverges into power downhibernation, low battery hibernation, and stable hibernation states.

While in stable hibernation state, MPAN-N enters general activationstate when wake-up 1 sequence (defined in 8.1) is detected. When MPAN-Nreceives RR packet, MPAN-N enters packet analysis state to probe onreceived RR packet. If the destination ID of the RR packet and MPAN-N ID(group ID or node ID) correspond, MPAN-N enters packet generation state.By sending an appropriate response packet to MPAN-C, MPAN-N entersstandby state. From standby state, MPAN-N will enter stable hibernationstate if it receives appropriate RA packet returned from MPAN-C; if itreceives RA packet for other nodes, MPAN-N returns to packet generationstate to send response packet again.

If MPAN-N detects error or mismatch during packet analysis (if the IDswill not correspond), MPAN-N enters hibernation power level detectionstate. MPAN-N may also enter hibernation power detection state fromstandby state when slot-number is not allocated before it is timed out;if MPAN-N is allocated of slot-number but has not received RA packetduring time-out period, or if MPAN-N has received RA for other MPAN-Ns,MPAN-N enters packet generation state. MPAN-N will regenerate andre-transmit response packet to MPAN-C, retuning to standby state. There-transmission of the response packet may be repeated for as much as Ntimes. On the N+1th time-out, MPAN-N enters hibernation power detectionstate. If RR packet arrives to MPAN-N while on the carrier detectionduring standby state, it enters packet analysis state.

If sensor system interruption occurs during stable hibernation state,MPAN-N enters general activation state. According to the command fromthe system, MPAN-N enters packet generation state. MPAN-N will generateand send appropriate data to MPAN-C, entering to standby state. IfMPAN-N receives DA packet, it returns hibernation power level detectionstate; if not, MPAN-N enters packet generation state to retransmitprevious data to enter standby state, until it will receive DA packet.If received DA is for other MPAN-Ns, the MPAN-N also returns to packetgeneration. On the N+1th time-out, MPAN-N enters hibernation powerdetection state.

7.3.2.2 Stabilization Procedure

MPAN-N undergoes a little more complicated states for WPT. MPAN-N instabilization will receive wake-up 1 (along with PTRq) during requestperiod, which wakes-up MPAN-N in stable hibernation state. MPAN-N willenter general activation state as MPAN-N receives PTRq packet, andpacket analysis state in consequence. If the ID in packet correspondswith node ID, MPAN-N goes to packet generation state to create PTRs. Attransmission MPAN-N enters hibernation power detection state. WhenMPAN-N receives PTBRq from MPAN-C, MPAN-N wakes up to general activationstate, analyzes to receive WPT from packet analysis state. If the packetis PTBRq, then MPAN-N probes on the packet and returns to hibernationpower level detection state. When MPAN-C sends PTS packet along withwake-up3, MPAN-N enters PSF activation state, then onto power statuspacket analysis state. According to the time schedule on the previousPTBRq, the path for MPAN-N diverges into two. One will lead MPAN-N topower reception right away, and the other will guide MPAN-N to powerisolation state to maximize overall WPT efficiency.

If MPAN-N has received PTS beacon and is scheduled for the followingtime slot, it will enter power reception state to receive WPT. Whenpower transfer finishes, MPAN-N enters hibernation power level detectionstate, before entering to stable hibernation state. From stablehibernation state, MPAN-N that has received PS beacon will go throughPSF activation, power status packet analysis and power status packetgeneration to create PSF. Sending PSF, MPAN-N will enter hibernationpower level detection state to appropriate hibernation state. MPAN-Nwill wait for next PTS or other relevant packets from hibernationstates.

If MPAN-N has received PTS beacon and is not scheduled for the followingtime slot, MPAN-N enters power isolation state. When PSFI begins, MPAN-Nin power isolation state enters hibernation power level detection state.MPAN-N will wait for PS beacon to go through PSFI procedures. MPAN-Nwill wait for next PTS or other relevant packets from hibernationstates.

7.3.2.3 Invigoration Procedure

MPAN-N in low power hibernation state may request for power transferduring spontaneous period: invigoration. While in low power hibernationstate, MPAN-N may detect wake-up 2 signal and enter low power packetanalysis state. If the packet is PTPC, MPAN-N enters low power packetgeneration state to generate PTRC to request for power transfer; MPAN-Nreturns hibernation power level detection state. As MPAN-N receivesPTEC, MPAN-N wakes to low power packet analysis state, then send PTECAfrom low power packet generation state to confirm power transfer. Aftersending PTECA, MPAN-N enters power reception state. When power transferfinishes, MPAN-N enters hibernation power level detection state, thenonto an appropriate hibernation state. The following PLRC will wakeMPAN-N to either low power packet analysis or to packet analysis state,depending on the power level of MPAN-N. MPAN-N will enter appropriatepacket generation state to send PLRCA, and enter hibernation power leveldetection. The power supplied at this time is of small amount, littleaffecting WPT originally intended for other MPAN-Ns.

7.3.2.4 Revitalization Procedure

When MPAN-N is in revitalization, MPAN-N is in power-down state. Thepower-down MPAN-N can receive power transfer automatically within MPANrange due to the nature of magnetic resonance. To make such proceduremuch effective, MPAN-C regularly broadcasts PTEC (no ack.) along withpower transfer during spontaneous. If power down device is turned on andenter low-battery hibernation state, MPAN-N will reply PLRCA to PLRCafter power transfer. From then on, MPAN-N engages in invigoration.

The states of MPAN-N are as described on FIG. 8.

8 Physical Layer Frame Format

8.1 General

This section describes the physical layer frame format of MPAN, adoptingthat of MFAN. As shown in FIG. 9, the PHY layer frame consists of threecomponents: the preamble, the header, and the payload. When transmittingthe packet, the preamble is sent first, the header follows, and finallythe payload comes last. An LSB is the first bit transmitted.

8.2 Preamble

As shown in FIG. 10, the preamble consists of two parts: a wake-upsequence and a synchronization sequence. An 8-bit wake-up sequence iscategorized in two types: one is for general MFAN communication, and theother one is for WPT. The wake-up 1 sequence for MFAN communicationconsists of [0000, 0000], and the wake-up 2 sequence for commandconsists of [1111 1111] and wake-up 3 sequence for WPT consists of [11110000]. The following 16-bit synchronization sequence consists of a12-bit sequence [0000 0000 0000]. A 4-bit sequence of [1010] comes afterthe synchronization sequence. The wake-up 1 sequence is only included inthe preamble of RR packet during the request period; the wake-up 2sequence is included in the preamble of PTEC packet during thespontaneous period; the wake-up 3 sequence is included in the preambleof PS beacon during the response period. The synchronization sequence isused for the packet acquisition, symbol timing, and the carrierfrequency estimation.

The preamble is coded using the TYPE 0 defined in 8.1.3. The wake-upsequence is modulated by ASK, but the synchronization sequence is codedusing BPSK.

8.3 Header

Specified in ISO/IEC 15149-1, 7.1.3

8.3.1 WPT Flag

The WPT flag frame of the header verifies whether the entire frame isfor WPT, or MFAN. If the frame has the value of 1, then it is for WPT;if it has the value of 0, then it is for MFAN.

8.4 Payload

Specified in ISO/IEC 15149-1, 7.1.4

8.5 Frame check sequence

Specified in ISO/IEC 15149-1, 7.1.5

9 MAC Layer Frame Format

9.1 General

The MAC frame of MPAN consists of frame header and frame body. Itinherits the MAC layer frame format justified in ISO/IEC 15149-1. Frameheader has information for data transmission to devices. Frame body hasthe actual data to be transmitted.

9.2 Frame Format for MPAN

All the MAC layer frames consist of frame header and frame body as shownin FIG. 11.

1) Frame header: Consists of the MFAN ID, frame control, source node ID,destination node ID, and sequence number. Frame header containsinformation for the transmission.

2) Frame body: Consists of the payload that contains actual data to betransmitted to MPAN devices and FCS used to check errors within thepayload.

9.2.1 Frame Header

Specified in ISO/IEC 15149-1, 8.2.1

9.2.2 Frame Body

Specified in ISO/IEC 15149-1, 8.2.2

9.2.3 Frame Type

There are four types of frame: request frame, response frame, dataframe, and acknowledgement frame.

TABLE 2 Frame type value Value Frame type (Binary) Content PeriodRequest frame 000 Request for the response of Request association (ARq),disassociation (DaRq), association status (ASRq), data transmission(DRq), power transfer (PTRq), power transfer beacon (PTBRq), and so on.Response frame 001 Response for the request of Response association(ARs), disassociation (DaRs), association status (ASRs), datatransmission (DRs), power transfer (PTRs), and so on. Data frame 010Data transmission without the Spontaneous request of coordinatorAcknowl- 011 Acknowledgement of the Response, edgement response (RA*)data Spontaneous frame transmission (DA), and command (CA) for nodesCommand frame 100 Command for power transfer Spontaneous permission(PTPC), power transfer execution (PTEC), power level request (PLRC) todevices *RA includes ARA, DaRA, ASRA, and so on

9.2.3.1 Request Frame

Specified in ISO/IEC 15149-1, 8.3.1

9.2.3.2 Response Frame

Specified in ISO/IEC 15149-1, 8.3.2

9.2.3.3 Data Frame

Specified in ISO/IEC 15149-1, 8.3.3

9.2.3.4 Acknowledgement Frame

Specified in ISO/IEC 15149-1, 8.3.4

9.2.3.5 Command Frame

The command frame consists of UID, command code, command block, and FCS.If the value for control code is 0, then it is WPT request; if the valueis 1, then it is WPT response.

9.2.4 Payload Format

Payload format is composed of request frame, response frame, data frame,and acknowledgement frame.

9.2.4.1 Request Frame

As shown in FIG. 13, payload for the request frame consists of group ID,request code, length, and more than one request block. When group ID is0xFF, it indicates that MPAN-C requests a response from all MPAN-Ngroups.

1) Group ID

Group ID field consists of 1 byte and is used to send RR packets tocertain groups. For the details of the group ID, refer to 6.4.3.

2) Request Code

Request code in payload of a request frame is shown in Table 3.

TABLE 3 Payload request code of request frame Request Category codeContent Remarks Network 0x01 Association Request for association requestresponse to unjoined nodes 0x02 Disassociation Request fordisassociation request response to joined nodes 0x03 Association Requestfor association status status request response to joined nodes 0x04-0x0FReserved — Data 0x11 Data request Request for data transmission tojoined nodes 0x12-0x1F Reserved — Configu- 0x21 Group ID set- Requestfor group ID change ration up request to joined nodes 0x22-0x2F Reserved— Wireless 0x31 Power transfer Request for power transfer Power requestresponse to joined nodes Transfer 0x32 Power transfer Request for powertransfer beacon request beacon to joined nodes 0x33-0x3F Reserved —Reserved 0x40-0xFF Reserved —

3) Length

Length field consists of 1 byte; it indicates the total length ofrequest block. The length field value is variable to the length and thenumber of request blocks.

4) Request Block

The data format of request block is composed differently according torequest codes; more than one request blocks can be included in thepayload of request frame.

The details for the data format of each request block are as follows:

a) Association Request

Specified in ISO/IEC 15149-1, 8.4.1.4

b) Disassociation Request

Specified in ISO/IEC 15149-1, 8.4.1.4

c) Association Status Request

Specified in ISO/IEC 15149-1, 8.4.1.4

d) Data Request

Specified in ISO/IEC 15149-1, 8.4.1.4

e) Group ID Set-Up Request

Specified in ISO/IEC 15149-1, 8.4.1.4

f) Power Transfer Request

The block format of PTRq is shown in FIG. 14. The first 2 bytes are forthe node ID of MPAN-N for PTRq. If the node ID is 0xFFFF, PTRq isrequested to all MPAN-Ns under the group ID. The next 1 byte is for theslot number. The last 1 byte is for the signal strength at transmissionfrom MPAN-C, and is measured in dB.

g) Power Transfer Beacon Request

The block format of PTBRq is shown in FIG. 15. The first 1 byte is forthe WPT ID of MPAN-N for PTBRq. If the WPT ID is 0xFF, PSBRq isrequested to all MPAN-Ns. The next 1 byte is for the slot number; next 2bytes for the length of power transfer frame; last 2 bytes for the powerlevel at transmission.

The last field, power transfer level, consists of significant figure and(n−2) power. Simply put to equation, the power transfer level is(Significant figure)*10^((n-2)) W.

9.2.4.2 Response Frame

The payload format of response frame has responsive information to therequest of MPAN-C. The response frame payload is shown in FIG. 16. Thefirst byte is for the group ID, the second byte is for the responsecode, the third byte is for the response date length (L), and the next Lbytes are for the response data.

1) Group ID

The group address field consists of 1 byte and is used to send RRpackets to a certain group. For the details of the group ID, refer to6.4.3.

2) Response Code

Response code types are shown in Table 4.

TABLE 4 Response code of response frame payload Response Category codeContent Remarks Network 0x01 Association Transmission of node UIDresponse 0x02 Disassociation Transmission of node UID response 0x03Association Transmission of node UID status response 0x04-0x0F Reserved— Data 0x11 Data response Transmission of requested data 0x12-0x1FReserved — Set-up 0x21 Group ID set- Transmission of UID and up responsegroup ID after changes in group ID 0x22-0x2F Reserved — Wireless 0x31Power transfer Transmission of requested Power response data to receivewireless Transfer power transfer 0X32-0x3F Reserved — Reserved 0x40-0xFFReserved —

3) Length

Length field consists of 1 byte and indicates the length of responsedata; it is variable according to the response data.

4) Response Data

Response data are divided into ARs, DaRs, ASRs, DRs, GSRs, and PTRs. Theresponse data format is as follows:

a) Association Response

Specified in ISO/IEC 15149-1, 8.4.2.4

b) Disassociation Response

Specified in ISO/IEC 15149-1, 8.4.1.4

c) Association Status Response

Specified in ISO/IEC 15149-1, 8.4.1.4

d) Data Response

Specified in ISO/IEC 15149-1, 8.4.1.4

e) Group ID Set-Up Response

Specified in ISO/IEC 15149-1, 8.4.1.4

f) Power Transfer Response

The block format of PTRs is shown in FIG. 17. The PTRs data consist of 2bytes for remaining amount of power in battery, 2 bytes for requiredpower level by node. The next 4 bytes are for the signal level: 2 bytesfor reception at node, and 2 bytes for transmission at coordinator.Probing on power levels and signal level, MPAN-C calculates distances toMPAN-N; efficient level of power may be transferred.

9.2.4.3 Data Frame

Specified in ISO/IEC 15149-1, 8.4.3

9.2.4.4 Acknowledgement Frame

The RA frame payload has data referring to the received response packet.The RA payload format is shown in FIG. 18. The first byte is for thegroup ID, the second byte is for the response confirmation code, thethird byte is for the length (L), and the next L bytes are for theresponse confirmation blocks.

1) Group ID

The group ID field consists of 1 byte and is used to send RR packets toa certain group. For the details of the group ID, refer to 6.4.3.

2) Response Confirmation Code

Response confirmation code types are shown in Table 5.

TABLE 5 Response confirmation code Reception confirmation Category codeContent Remarks Network 0x01 Association UID and assigned node responseID transmission of confirmation nodes 0x02 Disassociation UID and nodeID response transmission of confirmation nodes 0x03 Association UIDtransmission of status response nodes confirmation 0x04-0x0F Reserved —Data 0x11 Data response Confirmation of data confirmation transmissionto a joined node 0x12-0x1F Reserved — 0x21 Group ID UID and group IDset-up response transmission confirmation after group ID changes Set-up0x22-0x2F Reserved — Wireless 0x31 Power transfer Confirmation of Powerresponse power transfer Transfer confirmation response 0x32 Powertransfer Confirmation of execution power transfer command executtioncommand confirmation 0x33 Power level Confirmation of request powertransfer command request command confimation 0x34-0x3F Reserved —Reserved 0x41-0xFF Reserved —

3) Length

The length field consists of 1 byte; it indicates the length of responseconfirmation data and is variable according to the response confirmationdata.

4) Response confirmation block

Response confirmation block is divided into ARs confirmation, DaRsconfirmation, ASRs confirmation, DRs confirmation, and GSRsconfirmation. The block formats of the response confirmation are asfollows:

a) Association Response Confirmation

Specified in ISO/IEC 15149-1, 8.4.4.4

b) Disassociation Response Confirmation

Specified in ISO/IEC 15149-1, 8.4.4.4

c) Association Status Response Confirmation

Specified in ISO/IEC 15149-1, 8.4.4.4

d) Data Response Confirmation

Specified in ISO/IEC 15149-1, 8.4.4.4

e) Group ID Set-Up Response Confirmation

Specified in ISO/IEC 15149-1, 8.4.4.4

f) Power Transfer Response Confirmation

The block format for power transfer response confirmation is shown inFIG. 19. The first 2 bytes are for the destination node ID; the last 1byte is for the WPT ID to be assigned to.

g) Power Transfer Request Command Confirmation

The block format for power transfer request command confirmation isshown in FIG. 20. The first 2 bytes are for the destination node ID.Next 1 byte is for the command policy (accept if 0, deny if 1); the last1 byte is for the WPT ID to be assigned to.

h) Power Transfer Execution Command Confirmation

The block format for power transfer execution command confirmation isshown in FIG. 21. The first 2 bytes are for the destination node ID; thelast 1 byte is for the received power strength.

i) Power Level Request Command Confirmation

The block format for power level request command confirmation is shownin FIG. 22. The first 2 bytes are for the destination WPT ID; the last 1byte is for the received power strength.

9.2.4.5 Command Frame

The block format of command frame is shown in FIG. 23. The first 8 bytesare for the UID, next 1 byte is for the command code. Following L bytesare for the command block.

1) UID

UID field has 8 bytes in length.

2) Command Code

Command code defines the usage of command blocks. Only the code valuesfor WPT are defined at this point in time; other values are reserved forup to 30 functions to be included in the future.

TABLE 6 Command code of command frame payload Command Category codeContent Remarks Power 0x00 Power transfer Permission of transfer packettransfer startpermission in spontaneous period command 0x01 Powertransfer Request of wireless power request transfer from node in commandinvigoration 0x02 Power transfer Execution of wireless power executiontransfer from coordinator command 0x03 Power level Request for powerlevel request status of node command 0x04-0x0F Reserved — reserved0x10-0xFF Reserved —

3) Command Block

The format of command block is varied according to the command codeused. Only one command block may be appropriately used: either a requestor confirmation block.

The details of each command block is as follows:

a) Power Transfer Request Command

Power transfer request command block is composed of 2 bytes. First 1byte is for the power level, and the following 1 byte is for the time.

b) Power Transfer Execution Command

Power transfer execution command block is composed of 2 byte; it hasinformation of the time length of WPT.

c) Power Transfer Permission Command

The block for power transfer permission command is omitted; it isidentifiable from the header by putting appropriate value for its type.

d) Power Level Request Command

The block for power level request command is composed of 1 byte. It isidentifiable from the header, but specifies its destination by puttingWPT ID.

9.3 Frame Format for Power Status Feedback

All the frames of WPT consist of frame header and frame body as shown inFIG. 27.

1) Frame header: Consists of the Slot number, Frame control. Frameheader contains information for the transmission.

2) Frame body: Consists of the payload that contains PSF data to betransmitted to MPAN devices, and FCS that is used to check errors withinthe payload.

9.3.1 Frame Header

Frame header has information for the Power transmission Feedback

9.3.1.1 Total Slot Number

It includes the total number of slots; it has 1 byte.

9.3.1.2 Slot Number

It represents the current time slot number; it has 1 byte.

9.3.1.3 Frame Control

Frame control fields consist of frame type, frame policy; its format isshown in FIG. 28.

Each field is explained as follows:

1) Frame Type

Frame type field consists of 3 bits; refer to 9.3.3 for the details onframe types.

2) Frame Policy

TABLE 7 Frame policy Policy type value Content Response frametransmission policy 00 Request for the response No transmission Policy01 Request for no response

9.3.2 Frame Body

Frame body is variable in length and consists of payload and FCS. Eachpayload has a different format according to the frame type in the framecontrol field; FCS is used to check for errors in the frame.

9.3.2.1 Payload

The size of payload for WPT will range between 0 to 256.

9.3.2.2 Frame Check Sequence

FCS is 8 bits in length, and is used to verify whether frame body wasreceived without error. It is generated by using the following 8thstandard generator polynomial:

G(x)=x ⁸ +x ² +x ¹+1

9.3.3 Frame Type

Frame type field consists of 3 bits. There are two types of frames:request frame and response frame.

TABLE 8 Frame type Frame Type Value Content Period Power status beacon000 Power status beacon frame Response frame Power transfer start 001Power transfer start beacon Response beacon frame frame Power status 002Power status feedback frame Response feedback frame Reserved 010-111

9.3.4 Payload Format

9.3.4.1 PS Beacon

There is a PSFI during the response period of MPAN-C in between WPT.PSFI begins whenever a time slot for WPT to a certain MPAN-N or a groupends. It remains until MPAN-C receives all PSF frames from the MPAN-Ns.The frame format during the PSFI has short length and simple structureto avoid time waste while on WPT.

When PSFI begins, MPAN-C transmits PS beacon to have a quick update onpower status and abnormal situation. The request frame format is shownin FIG. 29.

1) Status Report

Status report determines process of PS beacon. The purpose of PS beaconis varied according to the usage of status report as shown on Table 9.

TABLE 9 Status report Value Frame status 0x00 Normal situation 0x01Abnormal situation 0x02-0xff Reserved

2) Number of WPT IDs

It is the number of WPT IDs which are enumerated in the frame body. Itrepresents the number of MPAN-Ns allowed to take WPT.

3) WPT ID

MPAN-C selects a certain MPAN-N or a group to respond to the PS beacon.In the PS beacon, WPT ID is used to shorten the length of beacon and tosimplify beacon structure. Details for the WPT ID are described in thesection 6.4.5.

9.3.4.2 Power Transfer Start Beacon

Block for power transfer start beacon is omitted; it is identifiablefrom the header by putting appropriate value for its type.

9.3.4.3 PSF

1) WPT ID

Specified in the section 6.4.5.

2) The Remaining Amount of Power in Battery

When MPAN-C requests battery information, MPAN-N sends information onthe remaining amount of the battery. 8 bits are reserved for the batteryinformation.

3) Received Power

For the efficient WPT scheduling, MPAN-N sends information on the powerreceived.

10 MAC Layer Function

10.1 General

In the MAC layer of MPAN, the following functions are considered toeffectively manage an MPAN: association, disassociation, ASC process,data transmission, group ID set-up, stabilization, invigoration, andrevitalization process. The MAC layer functions of WPT in stabilization,invigoration, and revitalization will be covered from MPAN; the othersare justified from ISO/IEC 15149-1, 9.

10.2 Stabilization

MPAN-C may send PTRq packet to MPAN-Ns. MPAN-Ns wishing to receive powerwill return PTRs packet to MPAN-C. According to the PTRs packetsreceived, MPAN-C will compute WPT schedule. Once schedule is set, MPAN-Cwill transmit PTBRq packet to all MPAN-Ns with schedule information.Soon after the transmission of PTBRq packet, MPAN-C also sends PTSbeacon, indicating the start of power transfer. On the basis of timeschedule from PTBRq, MPAN-N will enter power isolation state or powerreception state accordingly. When power transfer times out as scheduled,MPAN-C send PS beacon for power status updates; MPAN-N will reply withPSF. When all PSF frames are gathered, power transfer for the next timeslot begins.

If MPAN-C detects an error during WPT, MPAN-C stops WPT. MPAN-N while onWPT enters activation state when scheduled power transfer times out. Forbest certainty, response period is put to end for the superframe. Powertransfer will begin again from the next superframe when MPAN-C requestfor PTBRq.

10.3 Invigoration

If MPAN-N becomes low in power, MPAN-N may request power transfer fromMPAN-C even though it was not on the first priority. The MPAN-N low inbattery can receive a small portion of power, off from what wasoriginally being transferred to MPAN-N on the schedule.

When spontaneous period begins, MPAN-C sends PTPC to let MPAN-Ns low inpower request for power transfer with PTRC. Receiving PTRC, MPAN-C willsend PTEC (with ack.) to MPAN-N to transfer power in spontaneous period.If MPAN-N in low power properly reply PTECA to MPAN-C, then MPAN-Cstarts power transfer. The process will be repeated until MPAN-N entersstabilization. Whilst, MPAN-Ns in stabilization isolate themselves uponreceiving PTEC, so that power transfer in spontaneous period will be forlow invigoration and revitalization.

10.4 Revitalization

If the power of MPAN-N is completely dry out and powered off, the MPAN-Nis able to receive WPT regardless of the control from MPAN-C. Onceenough power has been supplied and MPAN-N is automatically turned on,the MPAN-N enters low-power hibernation state directly; the followingstep is identical to the procedures of invigoration.

However, in order to effectively manage revitalization process, MPAN-Cregularly sends PTEC (no ack.) and power along with PLRC in spontaneousperiod. Power-down node may not reply to PLRC, but just turned onlow-power MPAN-N can promptly reply PLRCA to MPAN-C as soon as MPAN-N isrevived from the power and receive PLRC after every short power transferinterval. As soon as MPAN-C is informed of low power MPAN-N the processcarries on as invigoration.

11 Air Interface

11.1 Frequency

MPAN's center frequency (f_(c)) is between 80 kHz and 400 kHz; it couldbe 88 kHz, 128 kHz, and 370 kHz with a maximum tolerance of ±20 ppm.

11.2 Signal Waveform for WPT

FIG. 35 shows the waveform for WPT, and the envelope parameters aredefined in Table 10. A general sine waveform is used for WPT because itprovides high power transfer efficiency. Amplitude in Table 10 denotesthe amplitude of the envelope. The envelope amplitude is varied fromnegative variation M_(i) to positive variation M_(h) within 10% ofAmplitude.

TABLE 10 WPT envelope parameters Parameter Symbol Min. Max. Positivevariation M_(h) 0 0.1 Amplitude Negative variation M_(I) 0 0.1 Amplitude

A number of exemplary embodiments have been described above.Nevertheless, it will be understood that various modifications may bemade. For example, suitable results may be achieved if the describedtechniques are performed in a different order and/or if components in adescribed system, architecture, device, or circuit are combined in adifferent manner and/or replaced or supplemented by other components ortheir equivalents. Accordingly, other implementations are within thescope of the following claims.

What is claimed is:
 1. A method for receiving wireless power including awireless charging device, the method comprising: entering a hibernationpower level detection state as the wireless charging device is turnedon; detecting a power level of the wireless charging device in thehibernation power detection state; and diverging into a power downhibernation state, a low power hibernation state and a stablehibernation state according to the detected power level condition. 2.The method of claim 1, wherein the diverging into a power downhibernation state, a low power hibernation state and a stablehibernation state according to the detected power level conditioncomprises: entering the power down hibernation state when the detectedpower level is lower than a first threshold level; entering the lowpower hibernation state when the detected power level is higher than thefirst threshold level and lower than a second threshold level; andentering the stable hibernation state when the detected power level ishigher than the second threshold level.
 3. The method of claim 2,further comprising: entering a general activation state when wake-up 1signal is detected while in the stable hibernation state.
 4. The methodof claim 2, further comprising: entering a power status feedback statewhen wake-up 3 signal is detected while in the stable hibernation state.5. The method of claim 2, further comprising: entering a low powerpacket analysis state when wake-up 2 signal is detected while in the lowpower hibernation state.
 6. The method of claim 5, further comprising:entering a low power packet generation state when receiving a powertransfer permission command while in the low power packet analysisstate; and generating a power transfer request command to request forpower transfer.